This invention is directed to a polymer useful for molding into a circuit board substrate, said polymer comprising a select polyarylethersulfone. Also, this invention is directed to a circuit board molded from said polyarylethersulfone.
Polyarylethersulfones containing the following repeat units: ##STR1## are commercially available polymers which have a wide variety of end-use applications. These polymers are described in, for example, U.S. Pat. Nos. 4,175,175 (polymer I) and 4,008,203 (polymer II). Such end-use applications include the use of these polymers for molding into circuit board substrates. However, a circuit board substrate molded from polyarylethersulfone (I) has a heat distortion temperature which is generally too low for soldering temperatures such as those encountered in wave soldering. Circuit boards molded from polyarylethersulfone (II) have an acceptable heat distortion temperature but do not have, in some instances, acceptable platability. Acceptable platability requires good adhesion of electrolessly plated copper to the circuit board substrate.
U.S. patent application Ser. No. 391,422, filed June 23, 1982, filed in the names of J. E. Harris et al and titled "A Composition Useful for Making Circuit Board Substrates and Electrical Connectors", commonly assigned describes a blend of 40 to 90 weight percent of a poly (ether sulfone), i.e., such as that of formula (II), and 10 to 60 weight percent of a polysulfone, such as that of formula (I). The application also states that the polyarylethersulfones described herein may be used. A circuit board substrate molded from the resultant composition is stated to have improved plateability.
The polyarylethersulfones of this invention are more particularly described in U.S. patent application Ser. No. 451,192 filed in the name of L. M. Maresca and titled "Aromatic Amorphous Thermoplastic Polymers", on Dec. 20, 1982, commonly assigned.
In the present invention it has been found that the incorporation of specified amounts of the following type of monomer: ##STR2## in the synthesis of polyarylethersulfone (I), produces a polymer which is suitable for being molded into circuit board substrates. When metal is electroplated onto such circuit board substrates there is a high degree of adhesion of the metal to the circuit board substrate.